You should play https://www.kerbalspaceprogram.com/ to learn the mathematics of orbital dynamics required to launch something into the sun. It's really hard which is why many of our solar system probes need to bounce off other planets (aka "gravity assist") to get close to the sun.

The math might change once we get a space elevator and a solar sail since it would be cheaper to get things into orbit and then parachute them into the sun.

Another idea would be to bury it into a really deep hole (https://en.wikipedia.org/wiki/Deep_borehole_disposal) or a part of the tectonic plates that would quickly take it into the Earth's core (https://en.wikipedia.org/wiki/Ocean_floor_disposal).